1. Field of the Invention
This invention relates to slip sensing robot gripper systems, and relates more particularly to a robot gripper system, operating on the springback phenomenon, the high speed return to rest configuration (springback acceleration) of a resilient pad which is suddenly released after being deformed linearly when a lightly gripped object suddenly releases energy stored by linear deformation of the gripper pad, which can determine slipping of an object lightly to facilitate controlled gripping, controlled slipping and controlled sliding of objects.
2. Description of the Prior Art
There are a great number of robot gripper systems which have been deployed or at least described in publications, some with relatively sophisticated feedback and servo systems to facilitate grasping of objects without damage. Remote pickup devices normally depend upon a human operator for intelligent control via various sensing and servo devices. Operating alone, however, the robot normally does not have sufficient sensing or intelligence to make the necessary determinations for controlled slipping of objects.
Robots may be equipped with a variety of sensing mechanisms, including optical viewing, weight measuring devices, strain gages and length measuring devices, among others. A particular problem with these prior art devices, however, is that they are not sensitive to the complicated dynamics of initial slippage of a gripped object during the processes of pickup and release. The human hand-brain combination handles initial slippage easily and elegantly. A person may control the slippage of a pencil in hand, letting the pencil slip in a controlled slide so as to come to rest in the writing position.
Controlled slippage in robot grippers has not normally been deployed; there is no known body of slip sensing art in robotics upon which to build. Certain vehicle safety programs have included skid sensing devices, again without common deployment; skid sensing devices tend to be optimized for rotating wheels and cannot be used directly in robotic grippers.
The following are representative of the prior art:
U.S. Pat. No. 3,744,850, Bartholome, AUTOMATIC TRACTION CONTROL SYSTEM, July 10, 1973, shows a wheel slippage detector comprising an angular accelerometer and a linear accelerometer which press against one another to measure the ratio of wheel angular acceleration to vehicular linear acceleration. Closure of the loop is obtained by interrupting the vehicle ignition circuit to slow the vehicle upon detection of a skid, and to control flow of brake fluid, so as to control slippage for maximum braking efficiency.
U.S. Pat. No. 4,306,148, Ringwall et al., TACTILE SENSOR, Dec. 15, 1981, shows a tactile feel system for a robot, in which a number of pneumatic passages are each equipped with a resilient light reflective tab and an optical fiber, and deformations of the tabs, indicating the presence and shape of the object, may be sensed.
U.S. Pat. No. 3,904,234, Hill et al., MANIPULATOR WITH ELECTROMECHANICAL TRANSDUCER MEANS, Sept. 9, 1975, shows an array of electromechanical transducers for force and slip sensing. Slip sensors include " . . . rotatable disks . . . extending outwardly from the opposing jawfaces." Hill does not show any slip sensor operating on the springback phenomenon.
Japanese Patent No. 52-33253, Hoshino, shows a hydraulic technique for increasing pressure and moving the gripper upwards until no slip is sensed. Hoshino does not show any slip sensor operating on the springback phenomenon.
Japanese Patent No. 52-33254, Hoshino, shows a similar hydraulic technique for increasing pressure until no slip is sensed. Hoshino does not show any slip sensor operating on the springback phenomenon.
Japanese Patent No. 53-13767, Aoki, shows a pneumatic gripper which applies force controlled in response to position with respect to an array of photodetectors and light emitting elements. Aoki does not show any slip sensor operating on the springback phenomenon.
USSR author's certificate No. 433,023, Liberman et al., ROBOT MANIPULATOR, Urals Polytechnic Institute--Kirov, Nov. 18, 1974, shows a robot manipulator with an electromechanical position transducer for slip sensing. A mechanical belt in one gripper face rotates the stem of a potentiometer for slip sensing. This USSR author's certificate does not show any slip sensor operating on the springback phenomenon.